Plant Oils

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Ways of Extracting Oil

Cold Pressing:

  • Seeds are combined using a combine harvester
  • Seeds are taken to a factory & crushed
  • Crushed seeds are pressed to extract the oil
  • The impurities are removed & the oil is processed
  • This makes food oils

Distillation:

  • Plant parts are put into boiling water
  • The oil from the plants evaporates along with the steam
  • The vapour is condensed & collected
  • Water & impurities are removed
  • This makes essential oils ( for perfumes)
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Cooking with Oil & Hydrogenation

Vegetable oils are useful for cooking because of their high boiling point

Foods cooked in oil instead of water have more fat = a higher energy content

However, they can cause heart disease & other problems

Vegetable oils can be hardened to make them solids at room temperature- eg. butter:

  • The oil is reacted with hydrogen in a nickel catalyst at 60 degrees
  • One c=c double bond breaks & hydrogen is added to the broken ends of the bonds
  • Not all the c=c bonds are hydrogenated
  • The unsaturated oil becomes saturated
  • This is called Hydrogenation
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Saturation

Saturated fats:

  • No c=c double bonds
  • Very unhealthy

Unsaturated fats:

  • One or more c=c double bond in its molecules
  • Healthier than saturated fats

Monounsaturated fats:

  • One c=c double bond per molecule

Polyunsaturated fats:

  • More than one c=c double bond per molecule
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Unsaturated VS Saturated

Unsaturated:

  • Contains double bonds
  • Low melting point
  • Molecules dont fit well together
  • Attractions between the molecules are weak
  • The fat/ oil is a liquid

Saturated:

  • No double bonds
  • High melting point
  • Molecules fit together well
  • Attraction between molecules is strong
  • The fat/ oil is solid
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Emulsions

Emulsifiers

  • Mixes two liquids together that dont usually mix-eg. oil & water
  • The molecules in emulsifiers have two parts, one that is attracted to the oil, one that is attracted to the water
  • Hydrophillic - water loving (attracted to water)
  • Hydrophobic - water fearing (attracted to oil)

Some emulsions include:

  • Margarine
  • Ice cream
  • Bread

Immiscible: Don't mix

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